1. Field of the Invention
This invention relates to a powertrain of hybrid electric vehicles, particularly to a powertrain module that can be installed between and secured to an engine output and a transmission input.
2. Description of the Prior Art
Hybrid electric vehicles have both an internal combustion engine and an electric machine which are alternately, or in combination, used to propel the vehicle. A variety of different powertrains are used in hybrid vehicles such as a parallel configuration, in which the engine is connected to the motor by a disconnect clutch with the motor driving a torque converter input of an automatic power transmission. The transmission has an output which is connected to a differential coupled to the two driven wheels of the vehicle.
A need exists in the industry for a hybrid electric powertrain that includes a modular subassembly for use with a variety of engines and transmissions, such that the module can be installed between and secured to an output of one of a number of engines and to an input of one of a number of transmissions. The assembled powertrain may then be employed in a variety of vehicles.
The module would include a hydraulically actuated disconnect clutch, the electric machine and suitable power paths between the engine and electric machine to the transmission input. Preferably, the module provides for hydraulic communication from the transmission's hydraulic system to the clutch, a balance dam and the electric machine. The module would provide an oil sump containing hydraulic fluid delivered to the module, and a path for continually returning that fluid to the transmission's oil sump so that the transmission pump is continually supplied reliably with fluid.
Use of such a module requires a hydraulic system that supplies fluid from the second sump to the line pressure source and line pressure is unavailable as when the engine is turned off to conserve fuel while the vehicle is stopped. The hydraulic system would supply fluid from a sump in the module to the transmission sump when the volume of fluid in the transmission sump is low enough to risk air ingestion into the inlet of the transmission pump, as when the vehicle is stopped while on a grade whose slope causes fluid to be retained in the module sump.